Modified territreal environment by Muhammad Fahad Ansari 12IEEM14

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Muhammad Fahad Ansari 12IEEM14

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Modified territreal environment by Muhammad Fahad Ansari 12IEEM14

  1. 1. Terrestrial EnvironmentMuhammad Fahad Ansari 12IEEM14
  2. 2. surface soil, the vadosezone, and the saturated zone
  3. 3. Surface soils Surface soil (unsaturated) Scale can range from 10 to 100’s of metersVadose zoneSaturated zone shallow aquifers X intermediate aquifers Vadose zone (unsaturated) deep aquifers Capillary fringe (nearly saturated) Water table Spontaneous water movement Saturated zone
  4. 4. Components of a typical soil1) 45% mineral (Si, Fe, Al, Ca, K, Mg, Na) The two most abundant elements in the earth’s crust are Si (47%) and O (27%) Quartz = SiO2 Clay minerals are aluminum silicates Nonsilicates = NaCl, CaSO4 (gypsum), CaCO3 (calcite)2) 50% pore space OM3) 1 to 5% organic matter Mineral Pore space
  5. 5. Soil texture – this defines the mineral particle sizes that make up a particular soil. particle diameter Surface to volume ratio range (mm) (cm2/g) Sand: 0.05 – 2 mm 50 Silt: 0.002 – 0.05 mm 450 Clay: 0.0002 – 0.002 mm 10,000
  6. 6. Texture and pore size distribution Clay texture Loam texture Sand textureNumber of pores Number of pores Number of pores Fine Coarse Fine Coarse Fine Coarse The amount of clay and organic matter in a soil influence the reactivity of that soil because they both add surface area and charge. Because large amounts of clay make the texture of the soil much finer, the average pore size is smaller. Similarly fluids like water move more easily through large pores, not because the water molecules are too large, but because there is less resistance to water movement through larger spaces. Pore size distribution is important when one considers movement of fluids and of microbes through a porous medium. Protozoa and bacteria will have difficulty moving through even sandy porous media.
  7. 7. Pore size5% of themean pore 20 um 0.6-20 um 0.02–0.6 umdiameter Filtration is important when the size of the bacterium is greater than 5% of the mean diameter of the soil particles
  8. 8. Water movement and soil water potential Increasing distance from particle surface A mSoil water potential depends onhow tightly water is held to a soilsurface. This in turn depends on Soil airhow much water is present.Surface forces have waterpotentials ranging from – Capillary forces Surface forces10,000 to –31 atm. Soil particles FREE WATERCapillary forces have waterpotentials ranging from –31 to–0.1 atm. Optimal microbialactivity occurs atapproximately -0.1 atm. Gravitational forcesAt greater distances there islittle force holding water to the Soil airsurface. This is consideredfree water and movesdownward due to the force of 0% % Saturation of 100%gravity. the soil pore
  9. 9. Soil atmosphere The composition of the earth’s atmosphere is approximately 79% nitrogen, 21% oxygen, and 0.03% carbon dioxide. Microbial activity in the soil can change the local concentration of these gases especially in saturated areas. Composition (% volume basis)Location Nitrogen (N2) Oxygen (O2) Carbon Dioxide (CO2)Atmosphere 78.1 20.9 0.03Well-aerated surface soil 78.1 18 - 20.5 0.3 – 3Fine clay/saturated soil >79 0 - 10 Up to 10
  10. 10. Microorganisms in soil – an overview• minor role as primary producers• major role in cycling of nutrients• role in soil formation• role in pollution abatement
  11. 11. Numbers and types of microbes in typical surface soilsBacteriaCulturable counts 106 – 108 CFU/g soil HighestDirect counts 107 – 1010 cells/g soil numbersEstimated to be up to 10,000 species of bacteria/g soilActinomycetesCulturable counts 106 – 107 CFU/g soilGram Positive with high G+C contentProduce geosmin (earthy smell) and antibioticsFungiCulturable counts 105 – 106/g soil HighestObligate aerobes biomassProduce extensive mycelia (filaments) that can cover large areas.Mycorrhizae are associated with plant roots.White rot fungus, Phanerochaete chrysosporium is known for its ability to degrade contaminants.
  12. 12. Comparison of bacteria, actinomycetes, and fungi Bacteria Actinomycetes FungiNumbers highest intermediate lowestBiomass --- similar biomass --- largestCell wall --- PEP, teichoic acid, LPS --- chitin/celluloseCompetitiveness most least intermediatefor simple organicsFix N2 Yes Yes NoAerobic/Anaerobic both mostly aerobic aerobicMoisture stress least tolerant intermediate most tolerantOptimum pH 6-8 6-8 6-7Competitive pH 6-8 >8 <5Competitiveness all soils dominate dry, dominate high pH soils low pH soils
  13. 13. The Aquatic EnvironmentOutline: – Water cycle – Properties of water – Light and temperature in aquatic environments – Oxygen and carbon dioxide in water – Water movement in streams – Tides and estuaries
  14. 14. Water or hydrologic cycle
  15. 15. Water storages and fluxes
  16. 16. Physical properties of water•High specific heat: •Specific heat: number of calories necessary to raise 1 gram of water 1 degree Celsius•Peculiar density-temperature relationship:pure water most dense when at 4 degreesCelsius.
  17. 17. Physical conditions in the aquatic environment – Light –Temperature –Oxygen –Salinity –Acidity
  18. 18. Physical conditions: 1. Light• Some incident sunlight is reflected from the water’s surface• The lower the angle of the sun, the greater the reflectance The amount of light that penetrates the water’s surface varies with latitude, season• Light that does penetrate is absorbed by water molecules…
  19. 19. Fig. 4.6
  20. 20. • Different wavelengths penetrate to different depths• E.g. for visible light: – Red: most rapidly absorbed – Blue: least rapidly absorbed --> greatest penetration• Suspended particles in the water also absorb and scatter light --> reduces penetration even further
  21. 21. Physical conditions 2. Temperature• Water is most dense at 4oC• Lake in summer: – temperature drops with increasing depth – Stratification of water column • Epilimnion: warm surface water • Thermocline: rapid decline in temperature • Hypolimnion: cold, dense water (~4oC)
  22. 22. Temperature• Tropical lakes: thermocline all year• Temperate lakes: only in summer – Autumn: surface cools --> temperature becomes uniform throughout (~4oC) Mixing of all parts = fall turnover – Increased nutrient levels at the surface
  23. 23. Fig. 4.7
  24. 24. Temperature• Temperate lakes in winter – surface colder than 4oC – Bottom near 4oC• Temperate lakes in spring – Ice melts --> surface warms --> ~4oC throughout Spring turnover
  25. 25. Temperature• Oceans: never undergo complete turnover• Winter: thermocline rises• Summer: thermocline descendsBottom never mixes with top
  26. 26. Temperature• Flowing waters: temperature variable• Shallow waters: follow air temperature – Track changes slowly
  27. 27. Physical conditions: 3. Oxygen• Diffuses from air through surface• Solubility decreases as water temperature increases• Solubility decreases as salinity increases• Diffusion: 10,000 times slower than in airMixing of water by winds and currents is critical• Temperature stratification --> oxygen stratification
  28. 28. Oxygen Oceans: Highest conc. near surface (upper 10- 20m) – Photosynthesis – Wind mixing • Decreases to minimum at 500-1,000 m – Oxygen minimum zone – No turnover --> water never reoxygenated • Below 1,000 m : conc. increases again – Polar regions: surface (high conc.) waters cool, sink --> currents --> highly oxygenated deep waters carried to lower latitudes
  29. 29. Physical conditions: 4. Salinity• Flow of rivers into ocean: dissolved materials increase over time• Concentrations can’t increase beyond maximum solubility limit. – e.g. Ca2+ forms CaCO3 (limestone) – e.g. Cl- - highly soluble (max. 360 g/L) • Maximum not yet reached (today 19 g/L)• Total concentration of all salt in ocean: 3.5% or 35 ppt• Fresh water 0.065 to 0.3 ppt
  30. 30. Physical conditions: 5. Acidity
  31. 31. Factors affecting pH• Fresh water: underlying rock is important – Limestone: • raises pH • buffers against changes – Sandstone, granite • Lowers pH• Oceans: Na+, K+, Ca2+ raise pH – pH ~ 7.5-8.4
  32. 32. Effect of pH on living organisms• Direct effects: interference with physiological processes• Indirect effects: effect on other dissolved substances – E.g. Al3+: concentration increases below pH 5 • Insoluble at higher pH
  33. 33. Water MovementFast flow --> rocky bottom Slow flow --> silty bottom Increase in water volume  increase flow rate
  34. 34. The Terrestrial Environment Outline: • Life on land • Light and vegetation • Soils – formation – horizons – moisture holding capacity – ion exchange Readings: Ch. 5
  35. 35. …is a hostile environment• Living cells 75-95% water; must remain hydrated to survive• Water availability fluctuates with precipitation patternsConstraints:1. Desiccation• Terrestrial organisms have adaptations that reduce water loss, and/or replace lost water
  36. 36. 2. Structural support• Trees invest > 80% of their mass in supportive woody tissue• Animals: skeletons
  37. 37. Terrestrial env’t - constraints3. Temperature variations on land >> those in the water
  38. 38. Physical conditions1. Light availability
  39. 39. Leaf area index
  40. 40. Orientation of leaves
  41. 41. Daily distribution of light
  42. 42. Seasonal distribution of light
  43. 43. Soil1. Formation • Begins with weathering of rocks • Types of weathering: i. Mechanical --> breakup • Freezing / thawing • Erosion • Roots ii. Chemical • Oxidation • Acids • Rainwater acts as medium for reactions
  44. 44. Factors affecting soil formationI. Parent material • Bedrock, glacial till, eolian (wind-deposited), fluvial (water-deposited)II. Biotic factors • Roots – Increase mechanical weathering – Reduce erosion – Reduce leaching – Increase organic material (affects pH)
  45. 45. Factors affecting soil formationIII. Climate • Direct effects: temperature, winds, pptn • Leaching = movement of solutes • Indirect effects: via plant growthIV. Topography • Steep slope --> increased erosion, “soil creep”V. Time • From bedrock to soil: ~ 2,000-20,000 yrs
  46. 46. 2. Soil types• Colour reflects chemical composition – Black: high organic matter – Yellow-brown or red: Fe oxides – Dark purple: Mn oxides – White / gray: CaCO3, MgCO3, quartz, gypsum
  47. 47. Soil types• Texture reflects particle size – Components of soil: • Sand: 0.05 - 2.0 mm • Silt: 0.002 - 0.05 mm • Clay: < 0.002 mm
  48. 48. “Texture” = %, byweight, of sand, siltand clay Size: 0.002 - 0.05 mm Size: < 0.002 mm Size: 0.05 - 2.0 mm
  49. 49. Soil texture• Affects pore space --> air, water movement• Coarse texture (high sand, low clay): – Large pores – Rapid water infiltration, drainage• Fine texture (low sand, high clay): – Small pores – Poor aeration – High surface area – High compactability
  50. 50. Soil layers (“horizons”)
  51. 51. Moisture retention• When all the pore spaces between soil particles are completely filled with water, the soil is at field capacity• Clay soil: – small pores --> slow drainage – Total pore space actually > than sandy soil! (higher field capacity)• Capillary water = water held by capillary action – Difficulty of extraction increases as moisture content decreases – wilting point: no further extraction
  52. 52. Available water capacity (AWC) = field capacity - wilting point• Pure sand: 30-40% of volume = pores• Pure clay: up to 60% of volume = pores – Higher field capacity and higher wilting point• AWC highest in soils of intermediate texture (loams)
  53. 53. Ion exchange capacity Ion exchange capacity = total # of charged sites on soil particles within a volume of soil Al3+ > H+ > Ca2+ > Mg2+ > K+ = NH4+ > Na+

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